Many modern operating systems executing on a computer provide a virtual area, often called a “desktop,” that serves as a user interface into which visual content such as images, icons, menus, or application user interfaces may be drawn or visually rendered. The desktop, including its drawn visual content, may then be displayed onto one or more display devices connected to the computer.
A typical computer desktop may be of limited use, however, to visually impaired users, who may not be able to adequately perceive content as it is typically displayed onto a display device. Accordingly, some users use Accessibility Technology (AT) software applications, such as ZoomText™ 9.1 Magnifier/Reader, developed by Ai Squared, Inc., of Manchester Center, Vt., that facilitate visually impaired users' use of computers. For example, such AT applications can apply enhancements, such as color enhancements, highlighting, magnification, or other enhancements, to a computer desktop to help a visually impaired user more easily perceive displayed content.
In one mode of operation, as illustrated by FIG. 1, an AT software application may magnify a portion (also referred to as a “viewport”) of a computer desktop 101. In FIG. 1, the portion of the desktop inside viewport 103, rather than the full desktop area of desktop 101, is magnified and displayed on a display device 105. In the example of FIG. 1, although the viewport 103 is only a portion of the full area of desktop 101, it occupies the full display area of display device 105, thereby allowing for magnification of the content in the viewport.
The boundaries defining the viewport may be adjusted, thereby allowing a user to move a viewport to magnify or otherwise enhance a different portion of the desktop. The viewport may be moved, for example, when a user causes the mouse cursor to move to the edge of the current viewport boundary, which is taken as an indication that the user desires the viewport to be moved to display visual content beyond that edge boundary, and may be increased or decreased in size depending on the magnification level selected by the user.